1. Field of the Invention
The present invention relates to a magnetically levitated motor in which a rotor is magnetically supported in non-contact and rotatable manner. In particular, the present invention relates to improvements in the winding structure within a magnetically levitated motor.
2. Description of Related Art
Magnetic bearings have been used for supporting rotary members in non-contact manner. A typical conventional radial type magnetically levitated motor 101 is shown in FIG. 11. The conventional radial type magnetically levitated motor 101 is proposed which integrates functions as a magnetic bearing and a motor. This type of conventional magnetically levitated motor 101 developed so far includes a Lorentz force magnetically levitated motor 101 with a stator 103 including six concentrated coils arranged on an 8-pole rotor 102. In this magnetically levitated motor 101, rotor driving coils 104 are disposed at the same locations where the six bearing coils 105 are disposed, as shown in FIGS. 11-13, both of which occupy the space between the rotor 102 and the stator 103.
However, when the rotor driving coils 104 and bearing coils 105 are disposed in two stages in a radial direction, the space between the magnet 106 and the back yoke 107 becomes greater, which causes a waste in the space, and may make it difficult to secure a sufficient coil space. This leads to a problem that the torque and levitational force diminish.
The present invention provides a magnetic levitation motor that effectively uses the space that has conventionally been wasted to increase the torque and levitational force.
In accordance with one embodiment of the present invention, a magnetic levitation motor comprises: a stator and a rotor confronting to the stator, in which the rotor is supported in a freely rotatable and non-contact manner, wherein the rotor has a rotor magnet magnetized in multiple poles, and the stator has rotor driving coils disposed opposing to the rotor magnet for generating a rotational torque on the rotor, and bearing coils for generating a bearing force in a direction perpendicular to a rotational axis of the rotor, wherein the rotor driving coils and the bearing coils are arranged along a circumferential direction in a manner shifted with respect to one another to avoid overlapping with one another. A displacement sensor is provided for detecting displacement of the rotor with respect to a plane which is perpendicular to the rotational axis of the rotor, wherein currents flowing in the bearing coils are controlled in accordance with output of the displacement sensor to keep the rotational axis of the rotor at a predetermined position.
In the above magnetic levitation motor, the rotor driving coils and bearing coils are disposed generally on the same circumference, in other words, in the same radial distance from the rotational axis of the rotor, without being superposed with one another in a radial direction. This configuration increases (for example, doubles) the occupancy rate of the coils and therefore substantially increases the rotational torque and the levitational force. In this case, the two coil sets (i.e., the rotor driving coils and the bearing coils) may be disposed shifted by a regular angle with a mechanical angle (or an electrical angle). By doing so, the rotational torque and the levitational force can be controlled independently from each other. Also, in one embodiment, instead of increasing the occupancy rate of the coils, the gap distance between the rotor and the stator may be shortened to increase the magnetic flux density in the gap. This can increase the rotational torque and the levitational force. Alternatively, in another embodiment, instead of increasing the coil space, the number of turns may be kept unchanged, and the rotor-stator gap can be reduced. This would increase the magnetic flux density in the gap, which makes it possible to increase the torque and levitational force, just as in the case in which the number of turns is increased.
In accordance with one embodiment of the present invention, the stator and rotor may be arranged so as to constitute a planar confronting type motor.
In accordance with one embodiment of the present invention, the stator and rotor may be arranged so as to constitute a cylindrical confronting type motor.
In accordance with one embodiment of the present invention, the rotor driving coils and the bearing coils may have an identical shape.
In accordance with one embodiment of the present invention, the rotor driving coils and the bearing coils may be integrated by a common wire in which current for generating the rotational torque and current for generating the bearing force flow in a superposed manner through the common wire.
In accordance with one embodiment of the present invention, the stator and the rotor may be arranged in a planar confronting configuration, wherein two plane-shaped rotor magnets are arranged in a direction of the rotor axis of the rotor, the stators are disposed on both sides of the two plane-shaped rotor magnets to be interposed by the stators, and the rotor driving coils and the bearing coils are provided on both sides of each of the stators.
In accordance with one embodiment of the present invention, a pair of cylindrical rotor-stator sets may be arranged along a rotational axis of the rotors.
In accordance with one embodiment of the present invention, salient poles may be provided between the rotor driving coils and the bearing coils.
In accordance with one embodiment of the present invention, the number of poles of the rotor magnet may be eight, and the number of poles of the bearing coils of the stator may be six. In accordance with one embodiment of the present invention, the number of poles of the rotor magnet may be four, and the number of poles of the bearing coils of the stator may be six.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.